Eye cosmetics usage in the UK is commonplace. Despite its popularity, there is a lack of published literature exploring the ocular effects of eye cosmetic usage. The influence of eye cosmetics upon symptoms of dry eye and contact lens discomfort has been suggested but these links have not been established. Consequently, this thesis aims to establish any link between ocular comfort with eye cosmetic usage. This was achieved by conducting a survey which showed the use of eye cosmetics, particularly eyeliner, significantly reduced ocular comfort. Amongst cosmetic users, contact lens wearers did not experience significantly reduced ocular comfort compared to non-contact lens wearers. Eye care practitioners often report observations of eye cosmetics contaminating the tear film, even when the products are applied to peri-ocular skin, although these reports are anecdotal. This thesis demonstrates that cosmetic pencil eyeliner migrates most readily and maximally contaminates the tear film when applied along the inner lid margin. After two hours post-application, contamination of the tear film from pencil eyeliner was negligible. This finding led to a subsequent study which examined the clinical and immunological responses of the ocular surface following migration of cosmetic pencil eyeliner. Clinically, eyeliner pencil did not appear to induce signs of ocular surface inflammation. However seven consecutive days of eyeliner application along the inner lid margin increased lipid layer thickness and dry eye symptoms compared to when the eyeliner was applied to peri-ocular eyelid skin. Subclinical signs of ocular surface inflammation were investigated by examining the concentration of inflammatory cytokines, IL-6 and IL-8, in tear fluid. A small reduction of cytokine concentration was exhibited after one day of eyeliner use although concentrations returned to near baseline levels after seven days of use. In conclusion, pencil eyeliner is safe to use and does not appear to induce clinical or subclinical signs of inflammation when used for up to seven days consecutively. The causes of increased dry eye symptoms are undetermined and the longer term effects of eyeliner application remain unknown.